Apparatus, system and method for cascaded power conversion

Abstract

An apparatus, method, and system are provided for power conversion to supply power to a load such as a plurality of light emitting diodes. An exemplary apparatus comprises: a first power converter stage having a first power switch and a first inductive element; a second power converter stage having a second power switch and a second inductive element; a plurality of sensors; and a controller. The second power converter stage provides an output current to the load. The controller is adapted to use a sensed input voltage to determine a switching period, and is further adapted to turn the first and second power switches into an on-state at a frequency substantially corresponding to the switching period while maintaining a switching duty cycle within a predetermined range.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A method of providing power conversion for a load using a power converter, the method comprising:
 sensing a first parameter including an input voltage level of an input voltage to the power converter, wherein the power converter includes a first power converter stage coupled to a second power converter stage, wherein the first power converter stage includes a first power switch, and wherein the second power converter stage includes a second power switch; 
 sensing a second parameter including an output current of the power converter or a current of the second power switch; and 
 turning the first and second power switches into an on-state substantially concurrently and at a frequency substantially corresponding to a switching period. 
 
     
     
       2. The method of  claim 1 , further comprising determining the switching period based, at least in part, on a maximum switching period, a minimum input voltage level, and the sensed input voltage level. 
     
     
       3. The method of  claim 1 , further comprising:
 operating the first power converter stage in a discontinuous conduction mode; and 
 operating the second power converter stage in a continuous conduction mode. 
 
     
     
       4. The method of  claim 1 , further comprising determining the switching period as a switching interval that maintains voltage stress of the first power switch and the second power switch below corresponding predetermined levels. 
     
     
       5. The method of  claim 1 , further comprising maintaining a switching duty cycle within a predetermined range to maintain voltage stress of the first power switch and the second power switch below corresponding predetermined levels. 
     
     
       6. The method of  claim 1 , wherein the first power converter stage further comprises a flyback configuration, a buck configuration, or a double-buck configuration, and wherein the second power converter stage further comprises a buck configuration, a boost configuration, or a buck-boost configuration. 
     
     
       7. The method of  claim 1 , wherein the first power converter stage further comprises a transformer, and wherein the second power converter stage further comprises an inductor. 
     
     
       8. The method of  claim 1 , wherein the first power converter stage further comprises a first inductor, and wherein the second power converter stage further comprises a second inductor. 
     
     
       9. The method of  claim 1 , wherein the load comprises a light-emitting diode. 
     
     
       10. The method of  claim 1 , wherein the input voltage level is in a range of voltages from 90 V RMS to 264 V RMS. 
     
     
       11. The method of  claim 1 , wherein the first power converter stage further comprises a rectifier. 
     
     
       12. The method of  claim 1 , wherein the first power converter stage further comprises a diode, and wherein the method further comprises:
 determining a switching period as a switching interval that maintains voltage stress of the diode below a predetermined level; or 
 maintaining a switching duty cycle within a predetermined range to maintain voltage stress of the diode below the predetermined level. 
 
     
     
       13. The method of  claim 1 , further comprising determining the switching period based, at least in part, on the sensed input voltage level. 
     
     
       14. The method of  claim 13 , wherein said determining the switching period comprises accessing a look-up table that includes a plurality of switching period values corresponding to a plurality of input voltage levels. 
     
     
       15. The method of  claim 1 , further comprising turning the first and second power switches into an off-state. 
     
     
       16. The method of  claim 15 , wherein said turning the first and second power switches into the off-state is in response to an increase in the first parameter. 
     
     
       17. The method of  claim 1 , wherein the switching period corresponds to a first threshold and to a second threshold, and wherein turning the first and second power switches into an on-state is in response to a decrease in the first parameter to the second threshold. 
     
     
       18. The method of  claim 17 , further comprising determining the first threshold and the second threshold based, at least in part, on a predetermined reference current level, a predetermined current variance level, a minimum input voltage level, and the sensed input voltage level. 
     
     
       19. The method of  claim 17 , further comprising determining the first threshold and the second threshold based, at least in part, on the sensed input voltage level. 
     
     
       20. The method of  claim 19 , wherein said determining the first threshold and the second threshold comprises accessing a look-up table that includes a plurality of first and second thresholds corresponding to a plurality of input voltage levels. 
     
     
       21. A computer-readable medium having instructions stored thereon that, in response to execution by a computing device, cause the computing device to:
 sense a first parameter comprising an input voltage level of an input voltage to the power converter, wherein the power converter includes a first power converter stage coupled to a second power converter stage, wherein the first power converter stage includes a first power switch, and wherein the second power converter stage includes a second power switch; 
 sense a second parameter comprising an output current of the power converter or a current of the second power switch; and 
 turn the first and second power switches into an on-state substantially concurrently and at a frequency substantially corresponding to a switching period. 
 
     
     
       22. The computer-readable medium of  claim 21 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to determine the switching period based, at least in part, on a maximum switching period, a minimum input voltage level, and the sensed input voltage level. 
     
     
       23. The computer-readable medium of  claim 21 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to:
 operate the first power converter stage in a discontinuous conduction mode; and 
 operate the second power converter stage in a continuous conduction mode. 
 
     
     
       24. The computer-readable medium of  claim 21 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to determine the switching period as a switching interval that maintains voltage stress of the first power switch and the second power switch below corresponding predetermined levels. 
     
     
       25. The computer-readable medium of  claim 21 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to maintain a switching duty cycle within a predetermined range to maintain voltage stress of the first power switch and the second power switch below corresponding predetermined levels. 
     
     
       26. The computer-readable medium of  claim 21 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to turn the first and second power switches into an off-state. 
     
     
       27. The computer-readable medium of  claim 21 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to turn the first and second power switches into an off-state in response to an increase in the first parameter. 
     
     
       28. The computer-readable medium of  claim 21 , wherein the first power converter stage further comprises a flyback configuration, a buck configuration, or a double-buck configuration, and wherein the second power converter stage further comprises a buck configuration, a boost configuration, or a buck-boost configuration. 
     
     
       29. The computer-readable medium of  claim 21 , wherein the first power converter stage further comprises a transformer, and wherein the second power converter stage further comprises an inductor. 
     
     
       30. The computer-readable medium of  claim 21 , wherein the first power converter stage further comprises a first inductor, and wherein the second power converter stage further comprises a second inductor. 
     
     
       31. The computer-readable medium of  claim 21 , wherein the load comprises a light-emitting diode. 
     
     
       32. The computer-readable medium of  claim 21 , wherein the input voltage level is in a range of voltages from 90 V RMS to 264 V RMS. 
     
     
       33. The computer-readable medium of  claim 21 , wherein the first power converter stage further comprises a rectifier. 
     
     
       34. The computer-readable medium of  claim 21 , wherein the first power converter stage further comprises a diode, and wherein the computer readable medium further has instructions stored thereon that, in response to execution by the computing device, cause the computing device to:
 determine a switching period as a switching interval that maintains voltage stress of the diode below a predetermined level; or 
 maintain a switching duty cycle within a predetermined range to maintain voltage stress of the diode below the predetermined level. 
 
     
     
       35. The computer-readable medium of  claim 21 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to determine the switching period based, at least in part, on the sensed input voltage level. 
     
     
       36. The computer-readable medium of  claim 35 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to determine the switching period based, at least in part, on the sensed input voltage level based on information in a look-up table that includes a plurality of switching period values corresponding to a plurality of input voltage levels. 
     
     
       37. The computer-readable medium of  claim 21 , wherein the switching period corresponds to a first threshold and to a second threshold, the computer readable medium further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to turn the first and second power switches into an on-state in response to a decrease in the first parameter to the second threshold. 
     
     
       38. The computer-readable medium of  claim 37 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to determine the first threshold and the second threshold based, at least in part, on a predetermined reference current level, a predetermined current variance level, a minimum input voltage level, and the sensed input voltage level. 
     
     
       39. The computer-readable medium of  claim 37 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to determine the first threshold and the second threshold based, at least in part, on the sensed input voltage level. 
     
     
       40. The computer-readable medium of  claim 37 , further having instructions stored thereon that, in response to execution by the computing device, cause the computing device to determine the first threshold and the second threshold based, at least in part, on the sensed input voltage level based on information in a look-up table that includes a plurality of first and second thresholds corresponding to a plurality of input voltage levels.